1. Field of the Invention
The present invention relates generally to electrical wiring devices, and particularly to electrical wiring devices for lighting control.
2. Technical Background
The most basic kind of power control device provides an ON/OFF control for electrical lamps, fans, or other such devices. For example, a device of this type may include a two-position wall switch that is toggled between the ON position and the OFF position. A power control device may also be equipped with a dimmer or a speed control circuit that allows the user to adjust the amount of power delivered to the load to a desired level. These types of power control devices allow a user to adjust the amount of current delivered to an electrical load, such as a light or a motor. When the electric load is a lighting device, the power control device is commonly referred to as a dimmer. If the power control device is configured to control a motor, such as a fan motor, the power control device is referred to as a motor speed controller. Motor speed controllers are also used to control the speed of machinery such as power tools, electric drills, chair lifts, stationary machinery, and other such variable speed motor driven elements. Moreover, some power control devices provide a continuous adjustment whereas others provide discrete adjustment levels.
The dimming or fan speed control functionality may be implemented using a voltage divider in combination with a potentiometer. Power levels may be controlled by adjusting the resistance of the potentiometer to thereby adjust the voltage output of the voltage divider. The voltage divider is typically coupled to a solid state switch such as a thyristor, FET switch, a silicon-controlled rectifier, etc. Specifically, the voltage divider output determines when the solid state switch is ON or OFF during the AC line cycle. The duration of the ON time relative to the entire AC line cycle is sometimes referred to as the duty cycle; and the duty cycle ultimately determines the ambient light level or motor speed.
Power control devices are typically packaged in a wiring device form factor for installation in an outlet box. The exterior of the wiring device includes either screw terminals or wire terminals for subsequent connection between the AC power source and the load. The device is installed by connecting the wiring inside an outlet box to the appropriate screw terminals disposed on the exterior of the wiring device. The power control wiring device is then inserted into the outlet box and attached to the outlet box using one or more fasteners. A cover plate is installed to complete the installation. Thus, installation of a power control device is a somewhat involved procedure that typically requires the services of an electrician.
A consumer may buy a power control device for a variety of reasons. The consumer may require a device that can control a unit that includes a fan motor and lighting element. Alternatively, the consumer may require a three-way switch or a switch that includes dimming functionality. In addition to the aforementioned functionality, the consumer will also select a power control device with aesthetics in mind What is needed, therefore, is a power control device that may be used with a set of homologous user-actuation interface assemblies such that a user-actuation interface may be safely removed and replaced with another user-actuation interface assembly without having to remove the device from the outlet box and without the need for tools.